Apparatus and Method for Detecting and Driving Headphones Differentially in Mobile Applications

Abstract

An apparatus and method is disclosed for achieving improved sound quality from mobile ‘hifi’ playback devices by driving compatible headphones in ‘balanced’ or ‘differential’ mode via standard size headphone connectors on the device, while retaining full compliance with legacy jack connections and conventional headphones. When a headphone is connected, a smartphone may determine whether the headphone is one capable of accepting balanced audio signals, or one that uses a conventional 3-pole jack or a 4-pole CTIA or OMTP jack. For a headphone that accepts balanced audio signals, the four poles of a 4-pole jack are used to drive left and right audio channels, and inverted left and right audio channels. For conventional 3-pole or 4-pole jacks, switches in the smartphone adapt the audio output signals to the configuration expected by the headphone.

Description

[0001]This application claims priority from Provisional Applications Nos. 62 / 217,585, filed Sep. 11, 2015, and 62 / 309,924, filed Mar. 17, 2016, which are incorporated by reference herein in their entirety.FIELD OF THE INVENTION[0002]The present invention relates generally to mobile devices, and more particularly to driving headphones through an analog output port in such a mobile device.BACKGROUND OF THE INVENTION[0003]It is now common for people to listen to music using mobile devices such as smartphones or other mobile media players (collectively “smartphones”). Users have rapidly become accustomed to having music played back through such devices, and often tend to have their smartphones with them at all times. At least many, if not most, of these users want to be able to listen to music having high sound quality. Smartphone makers have recognized this, and many have introduced ‘hifi’ smartphones, and even based much of their marketing strategy on their ability to deliver better q...

AI Technical Summary

Benefits of technology

The patent describes a way to create a balanced stereo signal from a mobile audio device with an analog audio output socket. This is done by measuring the impedance between different poles in the socket and comparing them to known values for different types of sound reproduction devices. By identifying which type of device is connected, the method automatically provides the correct signals to create a high-quality balanced stereo signal. The technical effect of this patent is to enable mobile audio devices to produce high-quality stereo sound without the need for expensive equipment or complex setup procedures.

Problems solved by technology

While current smartphones are able to reproduce stereo music with high sound quality, they are typically sold with included headphones that tend to be of mediocre or even poor quality, thus limiting the user's musical experience.

However, the performance of even high quality headphones is typically limited by the performance of the connection from the audio output port on the smartphone to the headphone transducers, and how the audio signals are provided to the headphones.

This common grounding of the channels results in crosstalk and signal loss through the parasitic resistance of this shared signal ground return path.

While there are some specific circuit implementations that have been tried to mitigate these issues, for example where feedback to the amplifiers is taken from as close to the jack common ground point as possible, ultimately it is not possible to avoid the common grounding of the left and right signal return paths in a 3-pole connector.

Thus, all such known devices provide common ground signal return paths, and thus suffer from these described audio signal quality issues.

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